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+/*
+ Copyright 2012-2015, Yahoo Inc.
+ Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
+ */
+var path = require('path'),
+ vm = require('vm'),
+ appendTransform = require('append-transform'),
+ originalCreateScript = vm.createScript,
+ originalRunInThisContext = vm.runInThisContext;
+
+function transformFn(matcher, transformer, verbose) {
+
+ return function (code, filename) {
+ var shouldHook = typeof filename === 'string' && matcher(path.resolve(filename)),
+ transformed,
+ changed = false;
+
+ if (shouldHook) {
+ if (verbose) {
+ console.error('Module load hook: transform [' + filename + ']');
+ }
+ try {
+ transformed = transformer(code, filename);
+ changed = true;
+ } catch (ex) {
+ console.error('Transformation error for', filename, '; return original code');
+ console.error(ex.message || String(ex));
+ if (verbose) {
+ console.error(ex.stack);
+ }
+ transformed = code;
+ }
+ } else {
+ transformed = code;
+ }
+ return { code: transformed, changed: changed };
+ };
+}
+/**
+ * unloads the required caches, removing all files that would have matched
+ * the supplied matcher.
+ * @param {Function} matcher - the match function that accepts a file name and
+ * returns if that file should be unloaded from the cache.
+ */
+function unloadRequireCache(matcher) {
+ /* istanbul ignore else: impossible to test */
+ if (matcher && typeof require !== 'undefined' && require && require.cache) {
+ Object.keys(require.cache).forEach(function (filename) {
+ if (matcher(filename)) {
+ delete require.cache[filename];
+ }
+ });
+ }
+}
+/**
+ * hooks `require` to return transformed code to the node module loader.
+ * Exceptions in the transform result in the original code being used instead.
+ * @method hookRequire
+ * @static
+ * @param matcher {Function(filePath)} a function that is called with the absolute path to the file being
+ * `require`-d. Should return a truthy value when transformations need to be applied to the code, a falsy value otherwise
+ * @param transformer {Function(code, filePath)} a function called with the original code and the associated path of the file
+ * from where the code was loaded. Should return the transformed code.
+ * @param options {Object} options Optional.
+ * @param {Boolean} [options.verbose] write a line to standard error every time the transformer is called
+ * @param {Function} [options.postLoadHook] a function that is called with the name of the file being
+ * required. This is called after the require is processed irrespective of whether it was transformed.
+ * @returns {Function} a reset function that can be called to remove the hook
+ */
+function hookRequire(matcher, transformer, options) {
+ options = options || {};
+ var extensions,
+ disable = false,
+ fn = transformFn(matcher, transformer, options.verbose),
+ postLoadHook = options.postLoadHook &&
+ typeof options.postLoadHook === 'function' ? options.postLoadHook : null;
+
+ extensions = options.extensions || ['.js'];
+
+ extensions.forEach(function(ext){
+ appendTransform(function (code, filename) {
+ if (disable) {
+ return code;
+ }
+ var ret = fn(code, filename);
+ if (postLoadHook) {
+ postLoadHook(filename);
+ }
+ return ret.code;
+ }, ext);
+ });
+
+ return function () {
+ disable = true;
+ };
+}
+/**
+ * hooks `vm.createScript` to return transformed code out of which a `Script` object will be created.
+ * Exceptions in the transform result in the original code being used instead.
+ * @method hookCreateScript
+ * @static
+ * @param matcher {Function(filePath)} a function that is called with the filename passed to `vm.createScript`
+ * Should return a truthy value when transformations need to be applied to the code, a falsy value otherwise
+ * @param transformer {Function(code, filePath)} a function called with the original code and the filename passed to
+ * `vm.createScript`. Should return the transformed code.
+ * @param options {Object} options Optional.
+ * @param {Boolean} [options.verbose] write a line to standard error every time the transformer is called
+ */
+function hookCreateScript(matcher, transformer, opts) {
+ opts = opts || {};
+ var fn = transformFn(matcher, transformer, opts.verbose);
+ vm.createScript = function (code, file) {
+ var ret = fn(code, file);
+ return originalCreateScript(ret.code, file);
+ };
+}
+/**
+ * unhooks vm.createScript, restoring it to its original state.
+ * @method unhookCreateScript
+ * @static
+ */
+function unhookCreateScript() {
+ vm.createScript = originalCreateScript;
+}
+/**
+ * hooks `vm.runInThisContext` to return transformed code.
+ * @method hookRunInThisContext
+ * @static
+ * @param matcher {Function(filePath)} a function that is called with the filename passed to `vm.createScript`
+ * Should return a truthy value when transformations need to be applied to the code, a falsy value otherwise
+ * @param transformer {Function(code, filePath)} a function called with the original code and the filename passed to
+ * `vm.createScript`. Should return the transformed code.
+ * @param opts {Object} [opts={}] options
+ * @param {Boolean} [opts.verbose] write a line to standard error every time the transformer is called
+ */
+function hookRunInThisContext(matcher, transformer, opts) {
+ opts = opts || {};
+ var fn = transformFn(matcher, transformer, opts.verbose);
+ vm.runInThisContext = function (code, file) {
+ var ret = fn(code, file);
+ return originalRunInThisContext(ret.code, file);
+ };
+}
+/**
+ * unhooks vm.runInThisContext, restoring it to its original state.
+ * @method unhookRunInThisContext
+ * @static
+ */
+function unhookRunInThisContext() {
+ vm.runInThisContext = originalRunInThisContext;
+}
+/**
+ * istanbul-lib-hook provides mechanisms to transform code in the scope of `require`,
+ * `vm.createScript`, `vm.runInThisContext` etc.
+ *
+ * This mechanism is general and relies on a user-supplied `matcher` function that
+ * determines when transformations should be performed and a user-supplied `transformer`
+ * function that performs the actual transform. Instrumenting code for coverage is
+ * one specific example of useful hooking.
+ *
+ * Note that both the `matcher` and `transformer` must execute synchronously.
+ *
+ * @module Exports
+ * @example
+ * var hook = require('istanbul-lib-hook'),
+ * myMatcher = function (file) { return file.match(/foo/); },
+ * myTransformer = function (code, file) {
+ * return 'console.log("' + file + '");' + code;
+ * };
+ *
+ * hook.hookRequire(myMatcher, myTransformer);
+ * var foo = require('foo'); //will now print foo's module path to console
+ */
+module.exports = {
+ hookRequire: hookRequire,
+ hookCreateScript: hookCreateScript,
+ unhookCreateScript: unhookCreateScript,
+ hookRunInThisContext : hookRunInThisContext,
+ unhookRunInThisContext : unhookRunInThisContext,
+ unloadRequireCache: unloadRequireCache
+};
+
+